IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 The kinetics of grape aromatic precursors hydrolysis at three different temperatures

The kinetics of grape aromatic precursors hydrolysis at three different temperatures

Abstract

In neutral grapes, it is known that most aroma compounds are present as non-volatile precursors. There is strong evidence that supports the existence of a connection between the content of aroma precursors in grapes and the aromatic quality of wine1. Harsh acid hydrolysis is considered the better way to reveal the aroma potential of winemaking grapes, because transformations taking place during fermentation include relevant chemical rearrangements in acid media that are better predicted by acid hydrolysis2. The aim of the present work is to establish a methodology to evaluate the aromatic potential of the grape from the acid hydrolysis in anoxic conditions of its aromatic and phenolic fraction.
In this work, firstly two different samples of Grenache grapes aromatic and phenolic fraction (PAF) were extracted, followed by acid hydrolysis under strict anoxic conditions based on a previously developed methodology3. These PAFs were reconstituted in model wine and aged in duplicate under anoxic conditions at three temperatures: 75, 50 and 35 ºC. The aged model wines were collected at different sampling times 75 ºC (1h, 2h, 6h, 12h, 24h, 48h, 96h), 50 ºC (0.5, 1, 2, 5, 7, 10 and 14 weeks) and at 35ºC (0.5, 1, 5, 3.5, 6, 9 and 12 months).
Hydrolysates were extracted and analyzed by two different analytical methods: esters, free norisoprenoids, terpenoids, phenols, lactones, vanillins and cinnamates were analyzed by SPE-GC-MS4, while varietal thiols were analyzed by LC-QqQ-MS.
The hydrolysates obtained at 50 and 75ºC present sensory profiles congruent with olfactory nuances of unoxidized wine. In fact, the absolute concentration values ​​found for terpenes, lactones and norisoprenoids are within the normal values ​​expected in a wine, except for TDN, which appears in large quantities. However, phenols, derivatives of vanilla and varietal thiols especially 3-mercaptohexanol appear in much higher amounts than would be expected in a Grenache wine, possibly because this type of hydrolysis is capable of release a major part of aromatic potential of grape. Very few differences are observed in the hydrolysis profiles between the two samples. The hydrolysis profile at the same temperature is similar between the samples in most cases even though different amounts of volatiles are obtained. All compounds seem to hydrolyze following two types of behavior that can be explained by the combination of two phenomena: the generation of volatiles (hydrolysis and rearrangements) and the subsequent degradation at wine pH. For those compounds with congruent evolutions at the three different temperatures, a model able to predict the evolution of varietal volatiles at room temperature will be presented.

DOI:

Publication date: June 24, 2022

Issue: IVAS 2022

Type: Poster

Authors

Sánchez Acevedo Elayma1, Lopez Ricardo1 and Ferreira Vicente1

1Laboratory for Aroma Analysis and Enology (LAAE), Universidad de Zaragoza, Instituto Agroalimentario de Aragón (IA2) (UNIZAR-CITA), Zaragoza (Spain)

Contact the author

Keywords

aromatic and phenolic fraction (PAF), acid hydrolisis, aroma

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

Soil or geology? And what’s the difference? Some observations from the New World

Observational historical geology seeks to establish the evolutionary history of the surface of Earth. This approach is applicable not only to bedrock, but to the soft material that lies at the surface, the stuff called soil by most people. The geologic perspective provides a view of this material that is quite different from that of soil science, at least as practiced by many in America.

Towards faultless Grenache wines: impact of climate and maturity

Climate change is affecting wine production and inducing significant variability in wine composition between vintages.

Influence of cell-cell contact on yeast interactions and exo-metabolome

Alcoholic fermentation is the main step for winemaking, mainly performed by the yeast Saccharomyces cerevisiae. But other wine yeasts called non-Saccharomyces may contribute to alcoholic fermentation and modulate the wine aroma complexity. The recurrent problem with the use of these non-Saccharomyces yeasts is their trend to die off prematurely during alcoholic fermentation, leading to a lack of their interesting aromatic properties searched in the desired wine. This phenomenon appears to be mainly due to interactions with S. cerevisiae. These interactions are often negatives but remain unclear because of the species and strain specific response. Among the non-Saccharomyces yeasts, Lachancea thermotolerans is a wine yeast naturally found in grape must and well known as a great L-lactic acid producer and an aromatic molecules enhancer, but its behavior during alcoholic fermentation can be completely different in co-fermentation with S. cerevisiae in function of strain used.

CropManage online decision support tool for irrigation scheduling of vineyards

CropManage (CM) is an online decision support service (DSS) developed by the University of California, Division of Agriculture and Natural Resources for assisting farmers with efficiently managing water and nitrogen fertilizer to match the site-specific needs of their crops.

Modeling the suitability of Pinot Noir in Oregon’s Willamette Valley in a changing climate

Air temperature is the key driver of grapevine phenology and a significant environmental factor impacting yield and quality for a winegrape growing region. In this study the optimal downscaled CMIP5 ensemble for computing thegrowing season average temperature (GST) viticulture climate classification index was determined to spatially compute on a decadal basis predictions of the GST climate index and the grapevine sugar ripeness (GSR) model for Pinot Noir throughout the Willamette Valley (WV) American Viticultural Area (AVA). Forecasts for average temperature and a 220 g/L target sugar concentration level were computed using daily Localized Constructed Analogs (LOCA) downscaled CMIP5 historic and Representative Concentration Pathways (RCP) future climate projections of minimum and maximum daily temperature. We explore spatiotemporal trends of the GST climate classification index and Pinot Noir specific applications of the GSR phenology model for the WV AVA. Spatiotemporal computations of the GST climate index and Pinot Noir specific applications of the GSR model enable the opportunity to explore relationships between their computed values with one intent being to provide updated GST ranges that better align with current temperature-based modeling understanding of Pinot Noir grapevine phenology and the viticultural application of LOCA CMIP5 climate projections for the WV AVA. The Pinot Noir specific applications of the GSR model or the GST index with updated bounds indicate that the percent of the WV AVA area suitable for Pinot Noir production is currently at or near its peak value in the upper 80s to lower 90s of this century.